Hi, and welcome to LQ!
Ideally you'll burn the ISOs as that, under Nero for instance using
the special option to Burn Image file to disk.
If you a) burn the ISO to disk as a file you have gained nothing but
a backup of that ISO and b) burn the files inside the ISO to disk you
miss out on the bootable bits.
Look here for details:
http://www.linuxquestions.org/linux/answers/LQ_ISO
Cheers,
Tink